A model of computation and a language construct are considered in which global names are used, but all read and write operations are local

The Andrew File System is a location-transparent distributed tile system that will eventually span more than 5000 workstations at Carnegie Mellon University. Large scale affects performance and complicates system operation. In this paper we present observations of a prototype implementation, motivate changes in the areas of cache validation, server process structure, name translation, and low-level storage representation, and quantitatively demonstrate Andrews ability to scale gracefully. We establish the importance of whole-file transfer and caching in Andrew by comparing its performance with that of Sun Microsystems NFS tile system. We also show how the aggregation of files into volumes improves the operability of the system.

Andrew is a distributed computing environment being developed in a joint project by Carnegie Mellon University and IBM. One of the major components of Andrew is a distributed file system which constitutes underlying mechanism for sharing information. The goals of the Andrew file system are to support growth up to at least 7000 workstations (one for each student, faculty member, and staff at Carnegie Mellon) while providing users, application programs, and system administrators with the amenities of a shared file system.

Virtual machines have long been used for functional testing of operating systems and to obtain the services of multiple operating systems from a single machine. They have not been used for performance evaluation however, because the timing observed by a program executing in a virtual machine is unpredictable and dependent on such factors as system load, real operating system overhead, real scheduling, etc. System level performance evaluation of hardware and operating systems has typically been done by hardware prototyping and dedicated machine benchmarking.

We investigate the inference rules that can be applied to functional and multivalued dependencies that exist in a database relation. Three types of rules are discussed. First, we list the well known rules for functional dependencies. Then we investigate the rules for multivalued dependencies. It is shown that for each rule for functional dependencies the same rule or a similar rule holds for multivalued dependencies. There is, however, one additional rule for multivalued dependencies that has no parallel among the rules for functional dependencies. Finally, we present rules that involve functional and multivalued dependencies together. The main result of the paper is that the rules presented are complete for the family of functional and multivalued dependencies.

This paper describes the fundamentals and some of the details of task communication in DEMOS, the operating system for the CRAY-1 computer being developed at the Los Alamos Scientific Laboratory. The communication mechanism is a message system with several novel features. Messages are sent from one task to another over links. Links are the primary protected objects in the system; they provide both message paths and optional data sharing between tasks. They can be used to represent other objects with capability-like access controls. Links point to the tasks that created them. A task that creates a link determines its contents and possibly restricts its use. A link may be passed from one task to another along with a message sent over some other link subject to the restrictions imposed by the creator of the link being passed. The link based message and data sharing system is an attractive alternative to the semaphore or monitor type of shared variable based operating system on machines with only very simple memory protection mechanisms or on machines connected together in a network.

A new property of queueing discipline, station balance , seems to explain why some disciplines yield product form solutions for queues and networks using nonexponential service disciplines and other disciplines do not. A queueing discipline satisfies station balance if rates at which customers receive service at each position of the queue are proportional to the probability that a customer arrives at that position. Station and local balance in queues and networks of queues are investigated. In addition to characterizing local balance and product form, the results of the paper generalize previous results on local balance to arbitrary differentiable service distribution functions.